Australia have lost McGrath, Shane Warne and other outstanding players since then – and have spent 2013 in chaos. Last Monday, amid the circus, they fired their coach, Mickey Arthur, and replaced him with a man called "Boof". Yet the decision to appoint Darren Lehmann as their new coach could be the smartest idea Cricket Australia have had in a very long time.

McGrath, as astute now as he was magisterial on the field, is better equipped than most to comment on the recent fiascos. He is also intriguing company – whether reflecting on personal tragedy, fighting cancer or revealing a surprising new interest in contemporary art. Yet it feels imperative, in the predictable spirit of Ashes cricket, to persuade him first to cough up one of his assertive prophecies. It's never going to be "five-zip to us", not these days, but what is McGrath's hand-on-heart prediction?

"Um …" he hesitates, "when I was playing it was easy. But now I find it tough to make a prediction. I'm a very loyal, parochial Australian and I can never say we're going to lose a series. So I'm going to say it'll be a good, tough series."

"10-0?" McGrath echoes in mock indignation. "I don't think people in Australia even have nightmares that bad. No, it's going to be much closer than people think. I have no doubts we can regain the Ashes – but if we get off to a bad start it could be a very long summer."

McGrath, once England's arch-tormentor, can expect some good-natured flak. "Oh yeah," he concedes, before joking: "But I've got a safety net to get out of the country after the first two Tests."

"You look at that side and over the next two years we lost seven players. That's going to knock any team in a big way," says McGrath. "But I wasn't aware of the extent they'd allowed things to slip until it all blew up in India in March. The way the 'homework' saga was handled was pretty poor. There was no way anything like that could have happened under Steve Waugh. There would have been no turning up late or not doing this or that. When you let that discipline slip you're going to have big problems on the field. We had some big personalities but they really pulled together."

He is withering about the 2am bar-room punch David Warner threw at England's Joe Root last month. "With Warner's track record it's blowing up in his face. He needs to weigh up how much he wants to play international cricket. If he does, he's going to have to be a lot more disciplined in his off-field behaviour."

McGrath was in India when he heard Arthur had been sacked. "I was surprised by the timing but the more I think about it the more positive it seems. Something had to happen because the way things were drifting it would have gone from bad to worse. Arthur had a good record with South Africa but I wasn't overly impressed by the decision to appoint him. That's the parochial Aussie in me again."

Lehmann, naturally, can be more readily trusted. "I played quite a bit with Boof and he's pretty relaxed. But he's also old-school. He was a class player and he's done great things as a coach. I've talked to guys who've played under him at Queensland and in the IPL and they all think he's great. Players warm to him and respect him and he brings out their best. That's what this team needs. I actually think Australia have got the players to perform pretty well and win back the Ashes – as long as the selectors have enough guts to pick the right team.

"Our bowling attack has been our strength for a long time but the top four batsmen have struggled. Chris Rogers brings a wealth of experience and he knows English conditions well. They should pick him. And now that Brad Haddin is No1 keeper again that experience and old-school hardness will be great for this team."

McGrath likes Australia's pace attack – highlighting Peter Siddle's "immense improvement as the leader", James Pattinson's "match-winning enforcer role", and Mitchell Starc's "left arm swing with the new ball". The Ashes, however, could be influenced most by an English opening bowler, Jimmy Anderson, whom McGrath speaks of in the vein of one master assessing another.

"He's undoubtedly a quality bowler. I was always quite a big fan but, years ago, Anderson struggled when he went overseas and bowled with the Kookaburra rather than the Duke ball. But he's now a great bowler wherever he plays. I'm just very impressed with the way Jimmy Anderson goes about his business."

McGrath is less effusive about the old enemy. "They're not a bad unit," he says of England. Such faint praise echoes McGrath's miserly streak as a bowler. "You look back at their 2005 team and they were very confident. Even a few years ago they deserved their world No1 ranking. But they've dropped off a little and they're not the same team of a few years ago. Still, they'll be quietly confident."

Before the first Ashes Test in 2005 McGrath had taken 499 wickets. He describes the ensuing match at Lord's, and that gripping series, from a deeply personal perspective. "My parents split up when I was 16," he remembers, "and, while Mum came to a few Tests, Dad didn't make many. So I was glad he was at Lord's. Dad thought it was incredible but he loved the crowd interaction most. He sat with the Aussies and on the first day – when [Steve] Harmison was knocking us over – the crowd just gave it to the Australians. Then, when we came out and took quick wickets, the Aussies in the crowd gave it back to the English. Dad was fascinated. When I got my 500th wicket they found out he was my father and they were all congratulating him, both from Australia and England. The whole series was so vivid – even though, in my mind, the wrong team won."

McGrath laughs wryly but he is more modest when reminded that Australia only lost the two Tests which he missed through injury. "I dunno about that, mate. The thing that stands out for me was walking down the street and people coming up to me saying they'd never watched cricket before and suddenly they couldn't miss a ball. I remember Old Trafford on the last day [as Brett Lee and McGrath denied a rampaging Andrew Flintoff and Harmison in the final overs] when so many people couldn't get in. That atmosphere, and especially the cricket, made it the best series I ever played in."

Defeat was galling, but McGrath suggests, "we became a better side while England, having achieved what they wanted, fell away. We won the next Ashes, which was the last series for me and Warnie, 5-0. It was the perfect way to bow out."

His wife Jane died 18 months later, in June 2008, when her cancer returned with terrible vengeance. She and Glenn had set up the McGrath Foundation six years earlier and the growth of that charity to fund the nursing of breast cancer patients helped him accept her death when their children, James and Holly, were just eight and six. "The support has been incredible," McGrath says. "From four nurses we're now employing 84 and we've supported 20,000 families over the last four years. It blows me away."

McGrath remarried in 2011, after he met Sara in Cape Town. She was as oblivious as his first wife had initially been to his fame. When they first went out Jane used to be confused that, in public, people would shout McGrath's name. "Glenn's got a lot of mates," she observed. It needed one of Jane's best friends to explain to her that, "Glenn's as famous as Robert de Niro." The great fast bowler shrugs in amusement. "It was the same with Sara. She asked me what I did. I said: 'I play cricket.' She said: 'No, what do you do for a living?'"

Does he ever watch old footage of himself – just as a reminder to him and Sara of his exploits? "Sara is Italian, she grew up between the States and Sicily and she has lots of friends who know nothing about cricket. So there's a DVD we occasionally put on to show them what I did. But life has moved on."

Apart from riding his Ducati, which Sara's father brought him as an Italian-flavoured wedding present, and attempting to earn his helicopter license, McGrath is coaching fast bowlers in India and commentating. "When I retired there were two things I didn't want to do – coaching and commentating. Now I'm enjoying them both. Sara and I have also opened an art gallery, Mclemoi, in Sydney. We specialise in contemporary art. It's a natural progression from opening the bowling for Australia to running an art gallery, isn't it?"

Sara's enduring involvement in art has introduced McGrath to a new world – yet how does he replace the intensity of playing for Australia? "It's a tough one because nothing can match you being the man and going out there and doing the business. I loved everything that goes with leading the attack in international cricket. So, yeah, there's a hole but I still view myself as the same guy who left the countryside. I jump on my Ducati and escape the city. There's such freedom in that."

Riding his bike, on his own, McGrath is also spared having to make any more Ashes predictions. "Sometimes," he says with a last cackle, "that can be a bit of a relief…"

• Glenn McGrath will be writing for the Guardian throughout the back-to-back Ashes series. He will be speaking at Sifting through the Ashes on Wednesday 17 July 2013, 6.30pm-9.30pm, with Mike Selvey and Vic Marks. Tickets are available via guardian.co.uk/ashes-masterclass